Monochromatic Collimated Light Source for an Indoor Lens Efficiency Tester

One promising way to convert solar energy into electrical energy is the use of point focusing Fresnel lenses in order to concentrate sun light on solar cells. The Fresnel lenses typically consist of a transparent polymer sometimes processed on a supporting substrate like glass. Regarding the system's performance the optical efficiency of the Fresnel lenses directly scales the electrical output. To verify computer predicted concentrator performance, to quantify production deviations from the desired lens design and for quality control we have built an appropriate measurement setup meanwhile in the 5th generation. This Lens Efficiency Tester (LET) evaluates the sample's concentrated light with the help of a scientific charge couple device (CCD). Therefore, the lens is exposed to a monochromatic, collimated, continuous light with sun-like divergence. This light source and some correctional steps are described in this contribution.